The invention relates to a ventilation/feedwater switching apparatus for an endoscope, and more particularly, to such switching apparatus used in a medical endoscope which is adapted to be inserted into a coeliac cavity and which includes a bottomed tubular body disposed in a ventilation/feedwater path and a sliding valve body which is slidably fitted in the tubular body to perform switching between the ventilation and the feedwater that is supplied to the distal end of the endoscope.
As is well recognized, an endoscope is adapted to be connected to a water feeder which supplies water to clean an observation window disposed in the distal end of a portion of the endoscope which is inserted into a coeliac cavity, or to a ventilator which supplies air into the distal end to cause an inflation of the coeliac cavity to facilitate an observation. Accordingly, the endoscope is associated with a ventilation/feedwater switching apparatus to control the supply of either water or air from such units to the distal end of the endoscope.
FIG. 1 illustrates essential parts of a typical endoscope which is associated with such a ventilation/feedwater switching apparatus. Endoscope 1 includes a proximate operating end 2 located outside a coeliac cavity to permit a variety of operations to be achieved, a portion 3 contiguous with the operating end 2 and which is adapted to be inserted into a coeliac cavity, a distal end 4 located in contiguous relationship with the outer or distal end of the portion 3, an eyepiece assembly 5 projecting from the operating end 2, and a connecting tube 6 which connects the endoscope 1 with a ventilator (not shown) and a water feeder (not shown).
A ventilation path and a feedwater path are defined by a ventilation tube 7 and a feedwater tube 8, respectively, which extend through the connection tube 6 and the portion 3 successively. A ventilation/feedwater switching apparatus 9 is disposed within the proximate operating end 2 and connected with the tubes 7, 8. It will be noted that the both tubes 7, 8 are joined together adjacent to the outer or distal end of the portion 3 and are connected with an injection nozzle 10 which is disposed in the distal end 4.
FIG. 2 shows an exemplary construction of a conventional ventilation/feedwater switching apparatus 9. As shown, it comprises a bottomed tubular body 11 to which the ventilation tube 7 and the feedwater tube 8 are connected, a cylindrical sliding valve body 12 which is slidably fitted in the tubular body 11, a check valve body 13 of a resilient material and having one end fixedly connected to the tubular body 11 so as to open or close a valve opening 16 which is formed in a partition located toward the lower end of the tubular body 11, a coiled compression spring 14 urging the valve body 12 in a direction to project out of the tubular body 11, and a plurality of O rings 15 interposed between the tubular body 11 and the sliding valve body 12 to prevent water leakage.
It will be noted that around part of the outer peripheral surface, the sliding valve body 12 is formed with an elongate groove 12b which is engaged by a pin 11a projecting inwardly from the tubular body 11 to control the vertical position of the valve body 12.
Under its normal condition when the switching apparatus 9 is not operated, the resilience of the spring 14 urges the sliding valve body 12 upward, thereby closing the feedwater tube 8 and allowing the ventilation tube 7 to communicate with the tubular body 11 to permit flow of air from the ventilator into the tubular body 11. When an air discharge port 12a which represents the upper opening of a bore 12c formed in the sliding valve body 12 is open, the flow resistance of a channel extending through the discharge port 12a is less than the flow resistance of a channel extending through the check valve 13 and ventilation tube 7 to the distal end 4 of the endoscope 1, so that upon entering the tubular body 11, the air will find its way through the bore 12c to be discharged externally through the air discharge port 12a.
However, when the port 12a is blocked by a finger 17 as indicated in FIG. 2, the interruption of the air flow to the exterior through the port 12a causes an increase in the internal pressure within the tubular body 11. Thereupon, this air pressure acts on the check valve body 13 to cause it to be folded back around a thinner portion 13a thereof, thus opening the valve opening 16 to feed the air into the distal end 4 of the endoscope 1 through the ventilation tube 7.
When the sliding valve body 12 is pushed into the tubular body 11 while closing the air discharge port 12a with the finger 17, the valve body 12 then blocks the ventilation tube 7 on its inlet side, and a circumferentially extending groove 18 formed in the outer peripheral surface of the sliding valve body 12 moves into communication with the feedwater tube 8 on its inlet side, whereby the water from the water feeder is fed into the distal end 4 of the endoscope 1.
When the sliding valve body 12 is released, the resilience of the spring 14 returns the valve body to its upper position, whereby the inlet side of the feedwater tube 8 is blocked again while the inlet side of the ventilation tube 7 becomes open, allowing the air to be discharged through the port 12a. The ventilation/feedwater switching apparatus 9 now returns to its inoperative condition.
With the conventional apparatus 9 mentioned above, there is experienced the inconvenience that a fluid within the coeliac cavity, such as blood or another contaminant, may flow backward through the ventilation tube 7 to the operating end 2 where it may cause the check valve body 13 to be fixed or to stick by coagulation. Also, when the endoscope 1 is left out of service for a prolonged period of time, the valve body 13 may be held tightly around the valve opening 16, causing a failure to open the ventilation path. In the event of such occurrence, a remedy is effected with the described switching apparatus 9 by inserting a push rod 19 of a reduced diameter through the air discharge port 12a of the sliding valve body 12 so that the free end of the rod 19 may be driven against the valve body 13 to separate it from around the valve opening 16.
While this remedy removes the valve body 13 from sticking or adhesion with the valve opening 16, it is possible that the valve body 13 itself may be broken. In such instance, replacement or repair thereof is very troublesome. Specifically, since the valve body 13 is fixedly connected to the tubular body 11 toward its lower end, a troublesome operation is required in that the proximate operating end 2 must be disassembled and the tubular body 11 and ventilation tube 7 must be removed before the valve body 13 can be changed.